Controlled casing sleeve

ABSTRACT

Apparatus and method for completing the well drilled through a producing formation which is susceptible to compaction as fluid is produced or the pressure is relieved therefrom. Through the area of expected compaction, a cyclindrical sleeve surrounds the casing and is held thereto by an adhesive having less shear bond strength than normal well cement. When compaction occurs, the sleeve is forced downwardly, shearing the adhesive and leaving the main casing undisturbed.

111 ttes Pat 1 1 1 1 3,857,445

Mower 1 Dec. 31, 1974 CONTROLLED CASING SLEEVE 3,020,962 2/1962 Holmquist 166/242 3,179,168 4/1965 Vincent [751 Invent Lawrence Mower, Tulsa, Okla- 3,593,795 7/1971 Broussard 166/285 [73] Assignee: Amoco Production Company, Tulsa,

Okla. Primary Examiner--James A. Leppink [22] Filed: Mar 2 1973 Attorney, Agent, or Ftrm-John D. Gassett; Paul F.

Hawley [21] Appl. No.: 337,612

[57] ABSTRACT [52] US. Cl .1 166/285, 138/145, 166/442 Apparatus and method for completing the well drilled [51] 1111. C1 E211) 33/00 through a producing formation which is Susceptible to [58] Fleld 61 Search 166/285, 442, 277; Compaction as fluid is produced or the pressure is w 138/145 148 lieved therefrom. Through the area of expected com paction, a cyclindrical sleeve surrounds the casing and [56] References Cited is held thereto by an adhesive having less shear bond UNITED STATES PATENTS strength than normal well cement. When compaction 1,896,111 2/1933 Simmons 166/242 c u the sleeve s forced downwardly, shearing the 1,896,112 2/1933 Simmons 166/242 adhesive and leaving the main casing undisturbed. 2,851,112 9/1958 Buck 166/242 3,012,585 12/1961 OBrien, Jr. 138/145 7 Clan/"S16 Drawmg Figures Patented Dec. 31, 1974 2 Sheets-Sheet 1 FIG.2

IIA I h/v/ TL................W........U ..V..... ....H.H.Q......

FIG.4

Patentcd Dec. 31, 1974 FIG.6

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to well completions and, more particularly, to a method and apparatus for protecting a well casing set in or through a formation susceptible to compaction as fluid is produced therefrom.

2. Setting of the Invention Oil and gas are produced from underground formations through well bores drilled from the surface to the formation. The oil and gas are contained in the pores of underground rocks or sand. Many formations, particularly in the Louisiana Gulf Coast Area, are of such porous nature that as fluid is withdrawn therefrom, the weight of the overlying earth causes the formation to be progressively collapsed or compacted. This phenomenon has caused considerable difficulty in oil field work. In many cases, the casing is caused to collapse or buckle to the point where the well, or at least that portion of the well, has to be abandoned. The present invention describes a method and apparatus for reducing the damage to casing caused by such compaction.

3. Prior Art U.S. Pat. No. 3,020,962 issued to J. L. Holmguist, Feb. 13, I962, dealt with this problem. There the Patentee advanced his theory as to how compaction damaged or collapsed the casing. To combat the problem, he provides a lower casing portion comprising alternate plain and traversely corrugated sections. The corrugations each have a wall thickness substantially less than the casing proper and thus allow an intermediate casing portion to shorten substantially without decrease in the inner diameter of the casing as the formation is compacted.

U.S. Pat. No. 3,593,795 issued to Leo P. Broussard, Sr., on July 20, 1971, dealt with this problem in a different manner. There a well is drilled and casing is installed in the well. The casing, however, is provided with expansion joint means to prevent buckling of the casing when any compaction occurs in the area susceptible to compaction. The Patentee teaches that the easing is then firmly fixed in position in the well.

These two patents just briefly described, reflect the best prior art of which I am aware. However, I am not aware of either of these systems being employed in a field in a compaction area.

BRIEF DESCRIPTION OF INVENTION This is a method and apparatus for completing a well drilled in subterranean formations in which at least a portion of the formations are subject to being compacted as fluid is produced therefrom. I provide a section of casing with a sleeve means to form a modified casing section in which the sleeve means includes at least one cyclindrical sleeve element held to the casing by an adhesive means having less shear bond strength than normal well cement. I connect this modified section of casing into the casing string and lower it into the well bore until the modified section is at the same level as that portion of the formation which is subject to compaction. If more than one cyclindrical element is needed, there is provided a space between the ends thereof and this space is filled with a resilient or flexible seal.

BRIEF DESCRIPTION OF THE DRAWING Various objectives and a better understanding can be had of the invention from the following description taken in conjunction with the drawing in which:

FIG. 1 shows a diagrammatic cross section of a subsurface well completed in a conventional manner in an area susceptible to compaction.

FIG. 2 is similar to FIG. 1 but shows some compaction after a period of production.

FIG. 3 is similar to FIG. 1 and is subsequent to FIG. 2, and illustrates damage done to the casing.

FIG. 4 illustrates a well completed in accordance wih my invention.

FIG. 5 illustrates, in diagrammatic form, movement of the outer sleeve due to compaction.

FIG. 6 illustrates a longer section of the well completed in accordance with my invention utilizing the sleeve arrangement shown in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION Attention is first directed to FIGS. 1, 2, and 3 which show a prior art completion of a well in a formation susceptible to compaction and the resulting damages. Illustrated in FIG. 1 is a well bore 10 having casing 12 which is set therein. Well bore 10 is drilled through an abnormal pressure producing formation 14, which is loosely consolidated. Immediately above zone 14 is an under compacted shale zone 16. Cement 18 is provided between casing 12 and bore hole 10. Perforations 20 are also provided so that fluid can be produced from producing zone 14 into casing 12 which can be provided with conventional producing tubing, which is not shown.

FIG. 2 is quite similar to FIG. 1 but shows the condition of the well after a period of production. In this case, hydrocarbon production has been accompanied by sand production resulting in a void area 22 surrounding the casing in the vicinity of production. As the formation pressure is reduced in zone 14, water is free to leave the under-compacted shale l6 and the overburden pressure is transferred from the waterfilled pore space to the shale matrix. This overburden pressure is in turn transferred through the cement sheath 18 to the casing. If overburden pressure transfer is sufficient, casing failure will occur in the void area of the producing zone where casing is virtually unsupported. This damage is shown in FIG. 3. This portion of the well may be lost. If production is to continue, the well must be re-worked, side-tracked, or a new well drilled.

Attention is now directed to FIGS. 4, 5, and 6 which illustrate my method of protecting the casing from the damage illustrated in FIG. 3. As shown in FIG. 4, I install protective metal sleeve elements 24 about casing 12. Sleeve elements 24 can be made of steel. I secure sleeve elements 24 to casing 12 by an adhesive 26 which has a shear bond strength with casing 10 which is less than the shear bond strength of cement sheath 18 with sleeve 24. A suitable adhesive means is a properly formulated elastomer providing proper shear bond strength, resilience, and environmental compatibility. The ends of elements 24 are spaced from each other leaving a sufficient space to absorb movement of one sleeve element 24 with respect to another. This space is filled with a flexible insert and seal 28. The sleeve elements are attached to the casing at. the surface to form a modified casing section which is lowered into the well as a unit.

To illustrate movement between the sleeve and the casing, two points are designated A and A thereon in FIG. 4 at the same elevation inasmuch as in FIG. 4 there has been no movement of the sleeve elements with respect to the casing. FIG. 5 is quite similar to FIG. 4 except that here some compaction has occurred after a period of production which may occur within a few months or it may take years to occur. When compaction occurs, sleeve element 24 moves downwardly with respect to casing 12 by an amount indicated by the difference in position of reference point A on the casing and reference point A on the sleeve.

A multiplicity of sleeve elements 24 is applied to flush joint casing so as to extend throughout the vertical dimension of the producing formation and the under-compacted shale formations for as great a distance as compaction may reasonably be expected as a result of producing operations. One normally suitable vertical distance for which the sleeve section should be provided is shown in FIG. 6. There I have an upper protecting casing string 30 with shoe 32 set at a depth which is normally above the depth at which compaction will cause damage to the casing as accurate as can be determined by geologists and engineers. Inside casing 36, I hang, or otherwise suspend, producing casing string 12. This is a casing string which extends to the production zones and also through the corresponding undercompacted formations. I prefer to extend my sleeve elements 24 to within the bottom portion of protecting casing 30. I limit the top of cement sheath 18 to below the top 34 of protecting sleeve 24.

As I have provided protective sleeve elements throughout the area subjected to compaction upon production, I have provided protection for the casing 12. Any movement caused by compaction of the various formations will be transferred to the protective sleeve but the protective sleeve as it is forced down will merely shear the adhesive means 26 and leave the easing 12 unmoved. It is to be understood that when the well is first completed perforations 38 are through the casing 12 and the sleeve element 24. As sleeve element 24 moves downwardly, the perforations in the sleeve and in the casing will no longer be aligned. This will necessitate another perforation job. However, this should present no difficulty inasmuch as casing 12 has been protected and thus is not damaged. Therefore, tools can be moved in and out the full length of the casing.

A bonus benefit is also provided by installation of this device of mine. In primary cementing operations, it is sometimes necessary to hold pressure on the casing while waiting on the cement to set. Upon release of the pressure on the casing, a weakening of the bond between the casing and the cement may occur. Further, during stimulation operations when high pressures are exerted on the inside of the casing, the expansion of the casing caused by the high pressure may cause a failure of the cement sheath. However, in casing strings equipped with sleeves-as described herein, the resilient insert material and the adhesive bond will absorb the hoop stresses caused by the internal pressure inside the casing and prevent damage to the bond between the sleeve and the cement.

While the above invention has been described in detail, it is to be understood that various modifications can be made thereto without departing from the spirit or the scope of the invention.

I claim:

1. A method of completing a well drilled in a subterranean formation in which at least a portion of said formation is subject to being compacted as fluid is produced therefrom which comprises:

a. providing a section of casing with a sleeve means to form a modified casing section in which said sleeve means includes at least one cylindrical sleeve element held to said casing by means having less shear bond strength than normal well cement,

b. connecting said section of casing into a casing string,

c. lowering said casing string into said wellbore until said modified section is the same level as said portion of said formation which is subject to compaction.

2. A method as defined in claim 1 including the step of cementing said casing string firmly in position in said well with said cement at least around said sleeve means.

3. A method as defined in claim 1 including providing a plurality of sleeve elements with space between the ends thereof and providing a flexible seal in such space.

4. An apparatus for protecting a well casing in a well drilled in a subterranean formation in which at least a portion is subject to being compacted as fluid is produced therefrom, the apparatus comprising:

a string of casing cemented in said well and including a protecting section adjacent said compactable portion of said formation; said protecting section comprising at least one sleeve element surrounding said string of casing and an adhesive between said sleeve element and the outer wall of the casing for holding said sleeve to said casing, the shear bond strength of said adhesive being less than that of well cement used for cementing said string of casing.

5. An apparatus as defined in claim 4 including a plurality of sleeve elements with longitudinal spacing therebetween and a flexible seal inserted in each such spacing.

6. An apparatus as defined in claim 4 in which said adhesive is an elastomer.

7. As a new article of manufacture, a length of well casing adapted to be set in a well and cemented therein by well cement which comprises:

a section of casing,

a plurality of sleeve elements surrounding at least a portion of said section of casing and having an annular space therebetween, said sleeve elements spaced longitudinally from each other to form a space between the ends thereof,

an adhesive in said annular space, the shear bond strength of said adhesive being less than that of said well cement, and

a flexible seal provided in said space between the ends of said sleeve elements. 

1. A method of completing a well drilled in a subterranean formation in which at least a portion of said formation is subject to being compacted as fluid is produced therefrom which comprises: a. providing a section of casing with a sleeve means to form a modified casing section in which said sleeve means includes at least one cylindrical sleeve element held to said casing by means having less shear bond strength than normal well cement, b. connecting said section of casing into a casing string, c. lowering said casing string into said wellbore until said modified section is the same level as said portion of said formation which is subject to compaction.
 2. A method as defined in claim 1 including the step of cementing said casing string firmly in position in said well with said cement at least around said sleeve meAns.
 3. A method as defined in claim 1 including providing a plurality of sleeve elements with space between the ends thereof and providing a flexible seal in such space.
 4. An apparatus for protecting a well casing in a well drilled in a subterranean formation in which at least a portion is subject to being compacted as fluid is produced therefrom, the apparatus comprising: a string of casing cemented in said well and including a protecting section adjacent said compactable portion of said formation; said protecting section comprising at least one sleeve element surrounding said string of casing and an adhesive between said sleeve element and the outer wall of the casing for holding said sleeve to said casing, the shear bond strength of said adhesive being less than that of well cement used for cementing said string of casing.
 5. An apparatus as defined in claim 4 including a plurality of sleeve elements with longitudinal spacing therebetween and a flexible seal inserted in each such spacing.
 6. An apparatus as defined in claim 4 in which said adhesive is an elastomer.
 7. As a new article of manufacture, a length of well casing adapted to be set in a well and cemented therein by well cement which comprises: a section of casing, a plurality of sleeve elements surrounding at least a portion of said section of casing and having an annular space therebetween, said sleeve elements spaced longitudinally from each other to form a space between the ends thereof, an adhesive in said annular space, the shear bond strength of said adhesive being less than that of said well cement, and a flexible seal provided in said space between the ends of said sleeve elements. 